This invention relates to improvements in communications systems and, more particularly, to a cross-talk suppression apparatus with application to an optical communication system in which audio and video information are combined and transmitted over an optical link.
In a common type of television communication over an optical communication system, such as one employing a fiber optical link, an amplitude-modulated television video signal is combined with an audio-modulated FM carrier signal, the combined signal being utilized to drive a light-emitting diode. The light emitted from the diode, which contains the video and audio information, is carried over the optical link and then recovered at a receiver.
A problem which occurs in the described type of communication results from cross-talk between the video and audio portions of the information. In particular, the audio sub-carrier is modulated to some degree by video leaking into the audio channel, and this results in an undesirable noise or "buzz" in the sound that is ultimately produced. This problem, which is also sometimes known as "cross-modulation" or "intermodulation", can also take the form of amplitude, phase or frequency modulation of the sound subcarrier.
It is an object of the present invention to reduce this problem which occurs in prior art systems.